A report from the consumer magazine Which? Travel has highlighted the huge bills that can be incurred by cruise travellers who are taken ill during a voyage.

The study, to be published in full tomorrow, has thrown up some hefty bills, ranging from £154 as a result of forgotten blood pressure pills to £2,000 for a case of acute sinusitis. Cruise lines say charges are in line with UK private medical care, but a spokesperson from AXA said cruise doctors do charge more than you would see in a clinic overseas.

When asked to reveal their medical costs for basic treatments such as asthma attack or GP consultation all lines – P&O, Cunard, Fred Olsen and Princess Cruises – bar one, Royal Caribbean, declined.

Because cruises attract an older clientele, often with pre-existing medical conditions, it has been very much in the broader commercial interests of cruise lines to ensure that medical facilities on board are comprehensive and state-of-the-art, according to travel medicine expert Dr Richard Dawood.

“Cruise companies have invested heavily [in facilities]: it is now commonplace to find hospital-grade facilities on board, with resuscitation facilities, laboratory and imaging tests available, a pharmacy and specialist doctors and nurses," he said. "Many of the bigger cruise lines are US-owned and land-based care in the US, even for minor problems, can be very expensive and considerably more costly than the average UK passenger would ever expect.”

According to the report P&O and Cunard said all of their ships comply with the American College of Emergency Physicians Healthcare Guidelines for Cruise Ship Medical Facilities.

Dr Dawood said most NHS users have no idea of the true cost of medicines when purchased privately. “While most land-based pharmacies can keep costs down by carrying only a narrow stock, to be topped up frequently as new prescriptions require, this is not possible at sea: pharmacies must carry a large stock, catering to the needs of passengers around the world, each item having its own limited shelf life."

Medical evacuation by helicopter is not uncommon on cruise ships – the cost of an airlift, especially if the ship will incur sea days, could run into tens of thousands. It is worth checking the policy’s small print to find out the extent of any evacuation cover.

Dr Dawood added: “Although I understand why the costs can be high I would not like to be at the receiving end of any of the horrendous experiences reported in the Which? article, which suggest that some of the companies might be piling on the costs unduly - perhaps in anticipation of the fact that most costs will be recoverable from insurance."